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29
30 // A sample program demonstrating using Google C++ testing framework.
31
32 #include "sample1.h"
33
34 // Returns n! (the factorial of n). For negative n, n! is defined to be 1.
Factorial(int n)35 int Factorial(int n) {
36 int result = 1;
37 for (int i = 1; i <= n; i++) {
38 result *= i;
39 }
40
41 return result;
42 }
43
44 // Returns true if and only if n is a prime number.
IsPrime(int n)45 bool IsPrime(int n) {
46 // Trivial case 1: small numbers
47 if (n <= 1) return false;
48
49 // Trivial case 2: even numbers
50 if (n % 2 == 0) return n == 2;
51
52 // Now, we have that n is odd and n >= 3.
53
54 // Try to divide n by every odd number i, starting from 3
55 for (int i = 3; ; i += 2) {
56 // We only have to try i up to the square root of n
57 if (i > n/i) break;
58
59 // Now, we have i <= n/i < n.
60 // If n is divisible by i, n is not prime.
61 if (n % i == 0) return false;
62 }
63
64 // n has no integer factor in the range (1, n), and thus is prime.
65 return true;
66 }
67